1. Field of the Invention
The present invention relates to a calibration phantom for quality assurance of an image-based radiotherapy apparatus.
2. Description of the Related Art
With the rapid progress of scientific technology, medical devices are also rapidly progressing and previously impossible medical treatments and diagnoses are becoming possible one by one. Among these medical devices, there have been various kinds of imaging apparatuses to detect and diagnose the status of the patient's internal organs in detail.
Some examples of the imaging apparatuses are Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Single Phonton Emission Computerized Tomography (SPECT), and Position Emission Tomography (PET) apparatuses. All of these apparatuses play very important roles in the diagnosis and treatment of tumors.
The imaging device is selected depending on the purposes of the diagnosis in order to capture accurate and clear images, since the imaging technologies of CT, MRI, SPECT, and PET are different from each other and they have their own advantages and disadvantages.
The CT apparatus is a device taking images based on the differences of the X-ray attenuation coefficient according to changes of electron density and provides good quality of anatomical imaging information with little distortion of images The CT is especially excellent for bone structure images and can be used as a basic prescriptive imaging device for radiotherapy since its density of information can be used to calculate the appropriate treatment volume and dosage Because the imaging apparatuses are designed to take the images of various kinds of tumors which are directly connected with a patient's survivability, accurate and precise imaging quality must be securely provided so that the doctors make a correct decision.
Therefore, the hospital with the imaging apparatuses needs to confirm if the devices are working properly. The procedures for the quality assurance of a series of medical imaging operations include a variety of measurement and evaluation which are continuously processed for system evaluation and system maintenance in order to secure the accuracy of a variety of information provided by the medical imaging devices.
The normal quality of the medical imaging devices slowly deteriorate as time goes by and the calibration processes must be done for continued quality assurance. A real cause for the quality changes of the devices needs to be reflected in the maintenance process after checking the image quality regularly or irregularly. Consequently, better quality of imaging products can be continuously provided by the devices and severe problems can be prevented from occurring before they happen.
After recognizing the size and location of the tumor via the medical imaging devices, radiotherapy using radiation can follow in order to remove the tumor. Radiotherapy is executed by an expensive medical device called a linear accelerator. The linear accelerator is used as a standard device for radiotherapy since the emitted energy can be minutely controlled as well as it delivers a high-dose-rate X-ray and an electronic beam.
While the linear accelerator is used, the most important thing is that radiation is collectively delivered to a tumor area without reaching a normal tissue area. Even though an accurate treatment plan has been established, it cannot be completely prevented that radiation damages normal tissues because the status of the tumor, located inside the patient's body lying down on a couch during radiotherapy, cannot be observed in real time.
Accordingly, an image-based radiotherapy apparatus has been developed recently. The image-based radiotherapy apparatus is a kind of medical radiation treatment device combining an imaging device with a radiation treatment machine, and is expected to be the next generation radiotherapy apparatus because radiation treatment can be started without delay and radiation beam can be delivered to the target point accurately and while observing the status of the tumor located inside the patient's body lying down on the couch (without movement of the patient).
There is a problem with unestablished quality maintenance procedures up until now because the image-based radiotherapy apparatus is the latest, newest machine. There is no satisfactory quality maintenance system for ensuring the quality of the image-based radiotherapy device Therefore, the hospitals or the organizations using the newly installed treatment device create their own equipment or are supplied by the small/medium medical equipment companies with the equipment for conducting the quality assurance.